Time complexity in n bit array multiplication

Question

Consider an array multiplier for multiplying two n bit numbers. If each gate in the circuit has a unit delay, the total delay of the multiplier is ?

1. Θ(1)
2. Θ(logn)
3. Θ(n)
4. Θ(n^2)

Answer 1

If you see the image above you will notice that delay caused is diagonal to the array.
So the delay is approxiamtely sqrt(2)*(2n-1).
Which is Θ(n)

Answer 2

The no. of gates used in n bit array multiplier(nxn) is 2n-1. So. if every single gate takes unit delay, then total delay 0(2n-1)=0(n) It is of linear order