Identify the expression for the exponential model that shows the constant reduction of estimated time and cost for doubled production. N is the unit number. Tl is the time or cost for the first unit. TN is the time or cost for the Nth unit, and s is the learning curve slope parameter.

Multiple choice question.

TN $=$ T$1/$ Ns

TN $=$ T$1$Ns

TN $=$ T$1+$ Ns

TN $=$ Ns $/$ T$1$