A bill for ₹1,840 is paid in the denominations of ₹50, ₹20 and ₹10 notes. 50 notes in all are used. Consider the following statements :

1. 25 notes of ₹50 are used and the remaining are in the denominations of ₹20 and ₹10.

2. 35 notes of ₹20 are used and the remaining are in the denominations of ₹50 and ₹10.

3. 20 notes of ₹10 are used and the remaining are in the denominations of ₹50 and ₹20.

Which of the above statements are not correct? 

Which number amongst 2⁴⁰, 3²¹, 4¹⁸ and 8¹² is the smallest?

The digits 1 to 9 are arranged in three rows in such a way that each row contains three digits, and the number formed in the second row is twice the number formed in the first row; and the number formed in the third row is thrice the number formed in the first row. Repetition of digits is not allowed. If only three of the four digits 2, 3, 7 and 9 are allowed to use in the first row, how many such combinations are possible to be arranged in the three rows?

X and Y run a 3 km race along a circular course of length 300 m. Their speeds are in the ratio 3 : 2. If they start together in the same direction, how many times would the first one pass the other (the start-off is not counted as passing)?