4. A firm has invested $30000 in equipment with a 5 -year useful life, The machinery wint. A) 2640 B) 3510 C) 4340 D) 5120 (b) (10 pts) Compute the after-tox present worth. A) 1040 B) 1290 (C) 1580 D) 1830 (c). (10 points) Compute the after-tax present worth, if 20% bonus depreciation is used. A) 1040 B) 1290 C) 1580 D) 1830