Setting the resolution output in an export PNG script

I have created a simple script that loops through each artboard in an open illustrator document and exports it as a separate PNG file. All is working well except that I want to set the resolution to 150 dpi and not 72 dpi for production reasons. This is an option that you can set when exporting manually to PNG but I don't seem to be able to set it in the PNG options in the code, although the script runs without errors it ignores the resolution setting. Could someone let me know what I'm doing wrong, many thanks. Code as follows:

var doc = app.activeDocument;;//Gets the active document

var fileName = doc.name.slice(0, 9);//Gets the G Number

var numArtboards = doc.artboards.length;//returns the number of artboards in the document

var filePath = (app.activeDocument.fullName.parent.fsName).toString().replace(/\\/g, '/');

$.writeln("fleName= ",fleName)

$.writeln("numArtboards= ",numArtboards)

$.writeln("filePath= ",filePath);

var options = new ExportOptionsPNG24();

for (var i = 0; i < numArtboards; i++ ) {

    doc.artboards.setActiveArtboardIndex( i );

    option.resolution = 150;

    options.artBoardClipping = true; 

    options.matte = false;

    options.horizontalScale = 100;

    options.verticalScale = 100; 

    options.transparency = true; 

    var artboardName = doc.artboards.name;

    $.writeln("artboardName= ", artboardName);

        var destFile = new File(filePath + "/" + fileName + " " +  artboardName + ".png");

        $.writeln("destFile= ",destFile);

          doc.exportFile(destFile,ExportType.PNG24,options);

    }