Contribution in the calculation of NPV

I was given a question in exam where i had to calculate the NPV and i had only practised question where i had to inflate the Selling price, Variable cost, Fixed cost etc just like the pro forma i learned. However, in the question i was given the contribution for several years and i was also given variable cost and the rates to inflate the costs. I do not really remember the exact question but in case i get a question whereby i am not given sales revenue and there is contribution, how should i deal with the question please? Regards, Thank you.