A 4 bit ripple counter and a 4 bit synchronous counter are

A 4 bit ripple counter and a 4 bit synchronous counter are made by flips flops having a propagation delay of 10 ns each. If worst case delay in the ripple counter and the synchronous counter be R and S respectively, then

1. R = 10 ns, S = 40 ns
2. R = 40 ns, S = 10 ns
3. R = 10 ns, S = 30 ns
4. R = 30 ns, S = 10 ns

In ripple counter, delay 4T_d = 40 ns.
If synchronous counter are clocked simultaneously then its worst delay will be equal to 10 ns.