Answer
(a) less than
(b) $7.274MeV$
Work Step by Step
(a) We know that when three alpha particles fuse to form carbon-12, then the sum of the mass of individual particles is greater than the atomic mass of carbon-12. This difference in mass is because of the conversion of some amount of mass into energy. Thus, the mass of carbon-12 is less than the mass of the three alpha particles.
(b) We can calculate the required energy as follows:
$E=|\Delta m|c^2$
We plug in the known values to obtain:
$E=(0.007809u)(\frac{931.5\frac{MeV}{c^2}}{1u})c^2$
$E=7.274MeV$
