Estimate how much mass the sun loses through fusion reactions during its 10-billion-year life. you can simplify the problem by assuming the sun's energy output remains constant.

The rate of mass loss of the sun assuming that the energy output remains constant is 4.26 million metric tons per second.

In 10 billion years, the total mass loss is

10 x 10^9 years (365.4 days / 1year) (86400 second / 1 day) (4.26 million metric tons/second)

Solve this and you'll get the answer.