DFA to accept strings of a’s and b’s starting with the string ab

Obtain a DFA to accept strings of a’s and b’s starting with the string ab 

Transition diagram to accept string ab(a+b)*

So, the DFA which accepts strings of a’s and b’s starting with the string ab is given by M = (Q, Σ , δ, q₀, A) where

Q = {q₀, q₁, q₂, q₃}

Σ = {a, b}

q₀­ is the start state

A = {q₂}.

q3=Dead State