Zarek Company adopted the dollar$-$value LIFO inventory method as of January $1,$ year $2.$ A single inventory pool and an internally computed price index are used to compute Zarek$$s LIFO inventory layers. Information about Zarek$$s dollar value inventory follows:

Date At Base Year Cost At Current Year Cost

$1/1/$year $2$ $ $110,000$ $ $110,000$

year $2$ layer $ $40,000$ $ $70,000$

year $3$ layer $ $70,000$ $ $140,000$

What is the price index used to compute Zarek$$s year $3$ dollar value LIFO inventory layer?