GMAT Critical Reasoning (CR) | Re: In comparison to the standard typewriter keyboard, the EFCO

(D) The more training and experience an employee has had with the standard keyboard, the more costly it is to train that employee to use the EFCO keyboard.

The conclusion is : Therefore, replacement of standard keyboards with the EFCO keyboard will result in an immediate reduction of typing costs.
So what answer choice that links the EFCO and other keyboard with respect to typing cost and also at same time, if true, would weaken the conclusion.

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