How can I draw an additional horizontal grid line with a specific value in Google Bar chart (Not average value)

How can I draw an additional horizontal grid line with a specific value in Google Bar chart. The line I want to draw is not the average. It is a specific value.

What I am getting

What I need

How can I do this?

EDIT

This my data model:

var data = google.visualization.arrayToDataTable([
    ["Month", "Points", { role: "style" }, "TARGET GOAL"],
    ["Apr-19", 17, "#c4c4c4", 25], 
    ["May-19", 32, "#c4c4c4", 25], 
    ["Jun-19", 20, "#c4c4c4", 25], 
    ["Jul-19", 22, "#c4c4c4", 25], 
    ["Aug-19", 27, "#c4c4c4", 25], 
    ["Sep-19", 26, "#c4c4c4", 25], 
    ["Oct-19", 18, "#008600", 25], 
    ["Nov-19", 18, "#008600", 25], 
    ["Dec-19", 18, "#008600", 25], 
]);

And in options object I have this:

seriesType: 'bars',
series:{
   3: {
        type: 'line'
      }
}

Since 25 is the value I want to be rendered as a line and it is in the 4th position.

And finally

var chart = new google.visualization.ComboChart(document.getElementById("container_id"));

Am I missing something?

EDIT-2 Complete script:

google.charts.load("current", {packages:['corechart']});
google.charts.setOnLoadCallback(drawChart_ebcg_unitary);

function drawChart_ebcg_unitary() {
    var data = google.visualization.arrayToDataTable([
        ["Month", "Points", { role: "style" }, "TARGET GOAL"],
        ["Apr-19", 17, "#c4c4c4", 25], 
        ["May-19", 32, "#c4c4c4", 25], 
            ["Jun-19", 20, "#c4c4c4", 25], 
        ["Jul-19", 22, "#c4c4c4", 25], 
        ["Aug-19", 27, "#c4c4c4", 25], 
        ["Sep-19", 26, "#c4c4c4", 25], 
        ["Oct-19", 18, "#008600", 25], 
        ["Nov-19", 18, "#008600", 25], 
        ["Dec-19", 18, "#008600", 25], 
    ]);

    var view = new google.visualization.DataView(data);
    view.setColumns([0, 1,
             {
                calc: "stringify",
                sourceColumn: 1,
                type: "string",
                role: "annotation"
             },
        2]);

        var options = {
        chartArea: {
                    left: 50,
                    width: "90%",
                    height: 250
        },

        title: "",
        width: '100%',
        height: 350,
        bar: {groupWidth: "90%"},
        legend: {position: "none"},
        seriesType: 'bars',
        series:{
            1: {
                type: 'line'
            }
        },
        vAxis: {
            minValue: 0,
            title: 'SALES UNITS'
        },
        hAxis: {
            title: 'MONTH'
        },
        annotations: {
            textStyle: {
                fontName: 'Arial, sans-serif',
                color: '#000000',
                fontSize: 12,
                bold: true
            },
            alwaysOutside: true
        }
    };


    var chart = new google.visualization.ComboChart(document.getElementById("ecbg_unitary"));
    chart.draw(view, options);
}

jQuery(window).resize(function () {
    drawChart_ebcg_unitary();
});

EDIT 3: Average line
How can I make the average line (please see screenshot) value (25) to appear only once, i.e at the end of the line rather than showing it on every month's column. This needs to look similar as in the screenshot under (What I need) section. Please advise.