Each sunday, mario weighs himself. here are his weight changes over a 4-week period.

week: 1 2 3 4
weight change
(in pounds) -2.1 0.3 -1.7 -0.4

adding decimals how much has mario’s weight changed over the entire 4 weeks?

a. –3.9 pounds

b. 5.4 pounds

c. 3.2 pounds

d. –4.1 pounds