Answer:
78
Explanation:
two of the faces are found from the rectangle of sides 6 and 4:
2 * 6 * 4 = 48
two of the faces are found from the right triangle of legs 3 and 4:
2 * 0.5 * 3 * 4 = 12
finally one face is a rectangle of sides 3 and 6:
3 * 6 = 18
adding up is 48 + 12 + 18 = 78