An investor purchases $25,000 in mutual fund units on January 1st. On April 1st, he receives $580 in dividends and reinvests them in additional units. On July 1st, he purchases an additional $5,000 in units. At the end of the year, the value of his mutual fund units is $31,000. Assuming no other transactions have occurred, what would his capital gain be if he were to sell his units for $31,000?

a)$210.

b)$5,420.

c)$420.

d)$5,000.