5500 is the awnser I came up with
0.5 x 4 = 2 feet / 2 feet in 4 seconds
15 - 2 = 13
New depth: 13 feet
0.4 x 3 = 1.2 feet / 1.2 feet in 3 seconds
13 - 1.2 = 11.8
New depth: 11.8 feet
10,208 is the correct answer
137,638
+52,091
-------
189,729 ⇨ 189,730
