total instructions =1200
Time period of clk=max{1,2,1.5,3,2.5}=3ns
30% of the instructions are conditional branches.So total clk cycles required to execute (1200*$\frac{30}{100}$)=360 instructions=(3*360)=1080.Because a conditional branch instruction computes the target address and evaluates the condition in the third stage of the pipeline(leads to take 3 clk cycles for completing single instruction).
For remaining 70%,i.e (1200-360)=840 non branch instructions one required 5 clk cycle and others 839 required 1 clk cycle each.so total (5+839*1)=844 clks required.
so total (844+1080)=1924 clk cycles needed
Therefore average execution time of the program for 1200 instructions is =(1924*3)ns=5772ns
