Normally if all the stages would have taken 1 clock cycle as is the case with a normal pipelined execution, then number of clock cycles needed to execute 200 instructions would be= 1*5+199*1=204
now add instruction executes in 1 clock cycle, so it doesnt take up any extra time.
Division requires 5 clock cycles for execution, so number of stalls in the pipeline caused due to these 25 instructions= 4
So extra clock cycles needed by these 25 instructions= 25*4=100
Similarly multiplication requires 3 clock cycles in execute stage. So number of stalls for each of these 75 instructions= 2
So extra clock cycles needed by these 75 instructions= 75*2=150
hence total number of clock cycles needed= 204+100+150= 454