Two Chemicals React to Form Another Chemical $t$ (In Hours) Is Given By

Two chemicals react to form another chemical. Suppose that the amount of chemical formed in time $t$ (in hours) is given by
$$x ( t ) = \frac { 11 \left[ 1 - \left( \frac { 2 } { 3 } \right) ^ { 3 t } \right] } { 1 - \frac { 1 } { 4 } \left( \frac { 2 } { 3 } \right) ^ { 3 t } }$$
where $x ( t )$ is measured in pounds.
a. Find the rate at which the chemical is formed when $t = 4$ . Round to two decimal places.
b. How many pounds of the chemical are formed eventually?