Sort:  

a) 9cm
b) guess that makes (13.5-9)^2 = 20.25 * 3 = 60.75 cm^2

Hi @larryphang,
I'm kelly and here i am giving you easy way to claim free 50 WCX Coins.
WCEX is a brand new digital currency exchange and they are going to launch soon. As part of launch they are offering free 50 WCX coins which is of worth 5$. Use below link to create your account and claim free coins(you need to click on confirmation email).
https://wcex.co/?ref=ScopGJmB

Coin Marketplace

STEEM 0.20
TRX 0.13
JST 0.030
BTC 64752.70
ETH 3455.13
USDT 1.00
SBD 2.50