AMC 12 2007b Problem 8

Tom's age is $T$ years, which is also the sum of the ages of his three children. His age $N$ years ago was twice the sum of their ages then. What is $T/N$ ?

$\mathrm {(A)} 2 \mathrm {(B)} 3 \mathrm {(C)} 4 \mathrm {(D)} 5 \mathrm {(E)} 6$