Answer & Step-by-step explanation:
2. Total income = Income from first r rows + Income from other last rows
[(Price per first r rows' seat ) x (no of first r rows) x (no of seats per first r row) ] + [ (Price per other last rows' seat ) x (no of last rows) x (no of seats per last row) ]
= [ 20 x (r) x (no of seats per first r row) ] + [ 15 x (other last ie 'total - r' rows) x no of seats per last row
3. 20 x 16 x (no of seats per first r row) = 320 x (no of seats per first r row)
4. 15 x (other last ie 'total - 16' rows) x no of seats per last row