Mike can plow a field in 12 hours and his brother phil can plow it in 15 hours. how long will it take them to plow it if they use two plows and work together?

Koji is installing a rectangular window in an office building. the window is 823 feet wide and 534 feet high. the formula for the area of a rectangle is a=bh. what is the area of the window? enter your answer as a mixed number in simplest form in the box. $$ ft2