How to calculate number of sunday's in a given month and year?

Integer month = 10;  
Integer year = 2019;
Integer numberDays = Date.daysInMonth(year, month);
Integer noOfSun = 0;
for(Integer i=1;i<=numberDays ;i++)
{
    Date myDate = date.newInstance(year, month, i);
    Datetime dt = (DateTime)myDate;
    if(dt.format('EEEE' == 'Sunday')
    {
        noOfSun = noOfSun + 1;  
    }
}