L1B Visa Holder Green card Process

In L1B Visa and currently if the person is in US, is it possible the employer able to process Green card(GC) for L1B Visa holder ?? How much time will take to get an approval of I-140 and getting green card?? If the I-140 approved means within 2 years green card approved for L1B Visa holder. is the information is right or wrong? Please clarify/reply ??

Its not as simple as you think.

The Green card processing time depends on what category of GC is filed and your country of birth.