1.6 g CH₄(g) undergoes combustion at constant volume at 300 K, and 2.5 kcal of heat is released. The heat of combustion of 1.6 g CH₄(g) undergoing combustion at constant pressure and the same temperature will be:
a) Less than 2.5 kcal
b) Exactly 2.5 kcal
c) Greater than 2.5 kcal
d) Cannot be determined without additional information