Twenty years ago, the father's age was 4 times the age of his son, 4 years hence the father's age 2 times the age of his son. Find the present age of the father and the son.
Three persons buy cold drinks of different bands A, B, C. The first person buys 12 bottles of A, 5 bottles of B, 3 bottles of C. The second person buys 4 botties of A, 6 bottles of B and 10 bottles of C. The third person buys 6 bottles of A, 7 bottles of B and 9 bottles of C. If each bottle of brand A costs tk. 4, each bottle of B costs tk. 5 and each bottle of C costs 6, then find the total sum of money spent individually by three persons for the purchase of cold drinks.