Using the Unix command line with grep, what is the regular expression for a grade that can be 0.0, or in the range 0.7 4.0 That is, it must match:

1. The numeral 0, followed by a period, followed by a zero
2. Or the numeral 0, followed by a period, followed by any numeral in the set 7, 8, 9
3. Or the numeral 1-3 followed by a period, followed by any numeral
4. Or the numeral 4 followed by a period, followed by the numeral 0