Assuming that the conditions are standard and that the alkanes are in a gaseous state, then we can simply use stoichiometry and molar masses.
366 mL C5H12 x 1 mole C5H12/ 22.414 x 10^3 mL x 1 mole C5H8 / 1 mole C5H12 x 22.414 10^3 mL / 1 mole C5H8
= 366 mL of C5H12