Grandma’s Bakery sells single-crust apple pies for $6.99 and double-crusts pies for $10.99. The total number of pies sold on…

Grandma’s Bakery sells single-crust apple pies for $6.99 and double-crusts pies for $10.99. The total number of pies sold on a busy day Friday was 36. If the amount collected for all pies that day was $331.64, how many of each type were sold?