The Polynomial Function $\mathrm { I } ( \mathrm { t } ) = - 0.1 \mathrm { t } ^ { 2 } + 1.4 \mathrm { t }$

Multiple Choice

The polynomial function $\mathrm { I } ( \mathrm { t } ) = - 0.1 \mathrm { t } ^ { 2 } + 1.4 \mathrm { t }$ represents the yearly income (or loss) from a real estate investment, where t is time in years. After how many years does income begin to decline?

A) 6 yr
B) 14 yr
C) 7 yr
D) 9.33 yr