Query on counters


A 4 bit ripple counter and 4 bit synchronous counter are made using flipflops having a propagation delay of 10ns each.if the worst case delay in the ripple counter and the synchronous counter be R ans S then:
A)R=10 ns S=40 ns
B)R=40 ns R=10 ns
C)R=10 ns S=30 ns
D)R=30 ns S=10 ns


In synchronous counter all flip flop operate at one clock cycle so we need 10 nsec
In ripple carry counter in one clock we can change only one flipflop but the total delay would be 40 nsec