Which example would most likely decrease friction?

using cleats, rather than gym shoes, on a field

using shaving cream, rather than shaving on dry skin

using a wide parachute, rather than a narrow parachute, when skydiving

using sandpaper, rather than regular paper, on wood

The vector a? is 3.50 cm long and is directed into this page. vector b? points from the lower-right corner of this page to the upper-left corner of this page and has the components bx=-19.5 cm , by=25 cm. in the right-handed coordinate system, where the +x-axis directed to the right, the +y-axis toward the top of the page, and +z-axis out of the page, find the x-component of the vector product a? ×b? , measured in cm2.