Find the total mass of the given rod and the center of mass:

The length of a rod is 12cm and the measure of the linear density at a point is a linear function of the measure of the distance from the left end of the rod. THe linear density at the left end is 3g/cm and at the right end is 4 g/cm.

Edit: this is okay now

Answer:

mass:42 g

center of mass: 44/7 cm from the left end