Your height: 4'9" to 5'1" (144 to 155cm) approximatly (?).
Frame size = 19.25in/49cm
Comments:
Mountain Bikes: they are sturdy and designed to go everywhere including off-road. Good for rough riding. In general heavy and with deep thread tires slow on paved roads. Not good city bikes unless narrower and slick tires are installed.
18 speed: perfect to go everywhere including going up very steep hills. There are 3 front chain rings and 6 rear gears. - Derailleur: Shimano
Tires 26 x 1.75: medium width tires with small thread, for comfort on asphalt and occasional off-road.