Answer the questions based on following data.
The pages of a book are numbered $0, 1, 2 …$ upto $M, M >0$. There are four categories of instructions that direct a person in positioning the book at a page. The instruction types and their meanings are :
- NEW : Position the book at page No. $1$
- END : Position the book at page No. $0$
- ONWARD, $n$ :From the current page move forward by $n$ pages; if, in this process, page number $M$ is reached, stop at $M$.
- REGRESS, $n$ : From the current page, move backward by $n$ pages; if in this process, page number $0$ is reached, stop at page number $0$.
In each of the following questions, you will find a sequence of instructions formed from the above categories. In each case, let $n1$ be the page number before the instructions are executed and $n2$ be the page number at which the book is positioned after the instructions are executed.
ONWARD, $10$; ONWARD, $10$. Which of the following statements about the above instructions is true?
- $n2 - n1=20$ only if $n1=0$
- $n2 - n1=20$ if $M>20$ and $n1=1$
- $n2 - n1=10$ if $M=21$ and $n1=0$
- $n2 > n1$ if $M > 0$