If you have to fit three number 10 bars and 2 number 8 bars in a rectangular beam of 12 inch width you may need to use two rows.
Given;
beam is 24 inch deep, the steel stirrup used is number 4,a 1 1/2 inch.
concrete cover on both sides. Sketch how you will place the bars and calculate the location of the effective depth. Place as many bars in the lower layers as possible.