In Sipser, It is given Pg. 284
Let t(n) be a function, where t(n) ≥ n. Then every t(n) time non-deterministic single-tape Turing machine has an equivalent 2 O(t(n)) time deterministic single tape Turing machine
In the given proof, at end they conclude
O(t(n)bt(n)) = 2O(t(n)).
where b is the maximum number of legal choices given by N’stransition function
I am unable to understand how did they conclude so>