Which of the following statements is incorrect?

a$.$ A pull system aims to produce goods or ensure delivery of services well in advance of demand, often according

to a schedule or plan created from potentially inaccurate forecasts.

b$.$ In a push system, the goal is to run machines and processes at their full capacity to eliminate downtime.

c$.$ A pull system waits for the customer $($either the external customer or the next work center$)$ to signal a need for a

good or service before producing it to fulfill that need.

d$.$ The signal from the $$customer$$ in a pull system is sent visually up the various stages of production $($even up the

supply chain$)$ to signal what and when production and deliver are needed.