b. Bitcoin follows a gold mining process. Every 10 minutes, there will be a new block mined. Reward for each block mined is cut in half every four years. For the first 4 years (or first 4-year period), the reward for mining a new block is 50 bitcoins. How many bitcoins have been awarded in total over the second and the third 4-year periods (i.e. from end of the 4th year to the end of the 12th year)? Please show full workings in the space below