Need help with #7 and 8 ASAP

Will you chech and finish these for me, because i am stumped with them.

In a voltaic cell, electrons flow from the (positive/negative) to the (positive/negative) terminal.

Light from a sodium lamp passes through a diffraction grating that has 1000 slits per millimeter. the interference pattern is viewed on a screen 1.000 m behind the grating. the first (m = 1) two bright yellow fringes that are visible are 0.7288 m and 0.7300 m from the central maximum. what are the wavelengths of these two fringes?