A is polynomially reducible to B

Question

Let there be two problems $A$ and $B$
It has been proved that,$A<B$ i.e. $A$ is polynomially reducible to $B.$This polynomial
reduction is carried out in time of $O(n).$The problem $B$ can be solved in $O(n^{3})$ time.
what is the time taken to solve problem $'A'?$

$A)O(n)$         $A)O(n^{3})$             $A)O(2^{n})$        $D)$None of these

Comments

@Lakshman Patel RJIT When we say by above reduction A can be solved in O(n³) time, we don't know whether the time required is theta(n²) or theta(nlogn) or any other functions of n which are asymptotically smaller than n. These all are tighter bounds than that of n³.

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thanks

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time complexity of A= time to convert A to B + time to solve B

                               =O(n)+O(n³) =O(n³)