please show work

Although the learning curve never completely levels off to a horizontal line, if work standards are to be devel- oped, there must be a point at which, for all practical purposes, learning is said to have stopped. If we have an 80 percent learning curve and say that the learning effect will be masked by other variables when the improve- ment in successive units is less than 0.5 percent, at about what unit number can the standard be set