Turnover calculation for tax

For a trader of goods, the threshold limit for registration is Rs.40L, for service providers it is 20L.

Q1
I have turnover of 50L rs. This year , i crossed threshold of 40L for goods, gst is @ 18%, then how much GST should I pay?
A) 50L * 18%
B) (50-40)L * 18%


Q2
I have turnover of 100L rs. I want to opt for composition scheme as turnover is less than 150L, where tax rate is 1% (for manufacturer) then how much GST should I pay??
A) 100L * 1%
B) (100-40)L * 1%

Q3
I have turnover of 45L rs. I want to pay tax at 6% under notification 2/2019 CT (R) (similar to composition scheme for service providers that was newly introduced where 50L is limit) then how much GST should I pay??
A) 45L * 6%
B) (45-20)L * 6%