Solve each problem, and express the answer in scientific notation. a. (
5
×
1
0
−
5
)
+
(
2
×
1
0
−
5
)
(5×10
−5
)+(2×10
−5
) b.
(
7
×
1
0
8
)
−
(
4
×
1
0
8
)
(7×10
8
)−(4×10
8
) c.
(
9
×
1
0
2
)
−
(
7
×
1
0
2
)
(9×10
2
)−(7×10
2
) d.
(
4
×
1
0
−
12
)
+
(
1
×
1
0
−
12
)
(4×10
−12
)+(1×10
−12
)