The brain mass of a fetus can be estimated using the total mass of the fetus by the function b$=0\mathrm{.}22$m$^(0\mathrm{.}87),$ where m is the mass of the fetus $($in grams$)$ and b is the brain mass $($in grams$).$ Suppose the brain mass of a $21$g fetus is changing at a rate of $0\mathrm{.}28$g per day. Use this to estimate the rate of change of the total mass of the fetus, $($dm$)/($dt$).($dm$)/($dt$)=,$ g per day $($Round to five decimal places as needed.$)$