$4-91.$ An electronic device is available that will reduce this

year's labor costs by $$8,000.$ The equipment is expected to

last for $10$ years. Labor costs increase at a rate of $5\%$ per

year and the interest rate is $10\%$ per year. $(4\mathrm{.}12)$

a$.$ What is the maximum amount that we could justify

spending for the device?

b$.$ What is the uniform annual equivalent value $(A)$ of

the labor costs over the eight$-$year period?