#### Answer

Altitude 1: 21
Altitude 2: 63/5

#### Work Step by Step

We use trigonometry:
Altitude 1 $= \frac{21}{sin90^{\circ}}=21$
For the second altitude, we use the angle in the lower right hand corner, which we call x:
$sinx = \frac{BF}{21} \\ 3/5 = BF/21 \\ BF = 63/5$