From the coordinates given the area will be as follows:
Area=length*width
(4, -1), (-1, 4), (11, 16), and (16, 11).
length of the triangle is given by:
length=√[(16--1)²+(11-4)²]=18.4
width=√[(4--1)²+(-1-4)²]=√(25+25)=7.1
thus the area will be:
A=18.4×7.1
A=130.64 sq. units