Two y axis in core plot graph with different axis scales

I am programming a app where I have graph with two y axis and one x axis.left y axis has range from 0 to 20 so there are 20 majorTick axis.Right y axis has range from 0 to 10,so I want left y axis to be labelled for every alternate majorTickAxis.

here is my code snippet

//code
   CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)self.graph.defaultPlotSpace;
float xmax=10.0;
float xmin=0.0;
plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(xmin)      length:CPTDecimalFromFloat(xmax-xmin)];
float ymax=20.0;
float ymin=0.0;
float ymax2=10.0;
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(ymin) length:CPTDecimalFromFloat(ymax-ymin)];



// Grid line styles
CPTMutableLineStyle *majorGridLineStyle = [CPTMutableLineStyle lineStyle];
majorGridLineStyle.lineWidth = 0.75;
majorGridLineStyle.lineColor = [[CPTColor whiteColor] colorWithAlphaComponent:0.75];

CPTMutableLineStyle *minorGridLineStyle = [CPTMutableLineStyle lineStyle];
minorGridLineStyle.lineWidth = 0.25;
minorGridLineStyle.lineColor = [[CPTColor whiteColor] colorWithAlphaComponent:0.1];

CPTMutableLineStyle *redLineStyle = [CPTMutableLineStyle lineStyle];
redLineStyle.lineWidth = 2.0;
redLineStyle.lineColor = [[CPTColor redColor] colorWithAlphaComponent:0.5];                         

CPTMutableLineStyle *greenLineStyle = [CPTMutableLineStyle lineStyle];
greenLineStyle.lineWidth = 2.0;
greenLineStyle.lineColor = [[CPTColor greenColor] colorWithAlphaComponent:0.5];     

// Axes
CPTXYAxisSet *axisSet = (CPTXYAxisSet *)self.graph.axisSet;
CPTXYAxis *x          = axisSet.xAxis;
x.orthogonalCoordinateDecimal = CPTDecimalFromString(@"0");
x.majorIntervalLength = [[NSDecimalNumber decimalNumberWithString:@"1"] decimalValue];
x.minorTicksPerInterval       = 4;
x.labelOffset = 3.0f;
x.title         = @"Time";
x.titleOffset   = 20.0;
x.titleLocation = CPTDecimalFromFloat((xmax+xmin)/2);
x.majorGridLineStyle= majorGridLineStyle;
x.minorGridLineStyle