Volume of shale can be calculated if gamma ray index data is available using the following equation; V sh =0.083(2 3.71 GR -1) where; I GR =gamma ray index V sh =Volume of shale on the basis of the...

Volume of shale can be calculated if gamma ray index data is available using the following equation;

V_sh=0.083(2^3.71GR -1)

where;

I_GR=gamma ray index

V_sh=Volume of shale

on the basis of the following V_sh
cut-offs,formations are regarded as clean, Shaly,or shale zone.

For V_sh
<10 %,="" implies="" a="" clean="">

For V_sh
10-35% implies a shaly sand

For V_sh> 35% implies a shale zone

Write a PHP program to determine the type of formation.(Test the program for I_GR=1.8308,2.1513,and 2.3756)