An explosive material having mass$=6$ Kg was initially at rest.

After explosion, one fragment having mass$=$M$1=2$ Kg$$ comes out and moves with velocity V$1$f$=60$ m$/$s$.$

The other fragment having mass$=$M$2=4$ Kg moves out with velocity$$V$2$f$=\_\_\_$ m$/$s

$$

Group of answer choices

positive $60$

positive $30$

negative $60$

negative $30$