Which description is most accurate regarding the differences between manufacturers and service providers?

Question $19$ options:

a$)$

Service providers have more control over the amount of variability of the resources they use than manufacturers do$.$

b$)$

For service providers, measuring productivity is fairly straightforward, whereas for manufacturers measuring productivity is more complicated.

c$)$

Manufacturers can separate the production of a product from its actual use, whereas the service dimension requires closer contact with the consumer.

d$)$

The products of manufacturers tend to be more customized than those of service providers.

e$)$

Manufacturers make more contact with their customers when compared to service providers.