A woman drives an SUV that gets ​mi/gal (mpg). Her husband drives a hybrid that gets mpg. Every​ week, they travel the same number of miles. They want to improve their combined mpg. They have two options on how they can improve it.
Option​ 1: They can tune the SUV and increase its mileage by mpg and keep the hybrid as it is.
Option​ 2: They can buy a new hybrid that gets mpg and keep the SUV as it is.
Which option will give them a better combined​ mpg?