After birth, a baby's weight increased at a steady rate for several weeks.
A linear model of this situation contains the values (1, 7.2) and (6, 9.2), where x represents the number of weeks, and y represents the baby's weight, in pounds.
What was the baby's weight at birth?

A.0.4 of a pound

B.5 pounds

C.7.2 pounds

D.6.8 pounds