Combining Random Variables Practice Test

In a science lab, measurement error (in millimeters) comes from two independent sources. Let $X$ be the error from the scale calibration with $\mu_X=0.2$ and $\sigma_X=0.6$. Let $Y$ be the error from the observer’s reading with $\mu_Y=-0.1$ and $\sigma_Y=0.8$. Define $E=X+Y$, the total measurement error. Which statement about the combined variable is correct?

A phone’s battery percentage decreases during two independent time periods. Let $D_1$ be the percent drop during the morning and $D_2$ be the percent drop during the afternoon. Assume $\mu_{D_1}=22$, $\sigma_{D_1}=6$, $\mu_{D_2}=28$, and $\sigma_{D_2}=5$. Let $D=D_1+D_2$ be the total percent drop. Which statement about $D$ is correct?