$25.$ Because the quality loss function represents a closed$-$form mathematical solution to determining quality loss, it is difficult to include in the formulation all of those aspects of the manufacturing system that will benefit from the never$-$ending pursuit of variation reduction, viz which dimensions?

a$.$ Improved production management

b$.$ Increased flexibility$/$adaptability

c$.$ Enhanced environment for breakthrough

d$.$ More positive employee attitudes

e$.$ All of the above