# Star time on main sequence

## Homework Statement

A B0 star has a luminosity of ~ 16000 L(solar) and a mass of ~ 16 M(solar). Can you estimate the time on the main sequence for this star simply from considering the rest mass energy of the core of the star (~10% of the total, and fusion burns with an efficiency of about 0.7%) and its luminosity?

## Homework Equations

I know that for main sequence stars, L is proportional to M^3

## The Attempt at a Solution

I have no idea where to go with this question, i've trawled through so many webpages and textbooks without success. Any ideas?

Dick