When the outlier(s) are removed, how does the mean change?

dot plot with 1 dot over 50, 2 dots over 72, 1 dot over 74, 1 dot over 76, 1 dot over 78, 3 dots over 79, 1 dot over 80, 1 dot over 81, 3 dots over 82, and 1 dot over 83

The mean decreases by 1.9.
The mean increases by 2.4.
The mean increases by 1.9.
There are no outliers.

Here is their argument. given the obtuse angle x, we make a quadrilateral abcd with ∠dab = x, and ∠abc = 90◦, and ad = bc. say the perpendicular bisector to dc meets the perpendicular bisector to ab at p. then pa = pb and pc = pd. so the triangles pad and pbc have equal sides and are congruent. thus ∠pad = ∠pbc. but pab is isosceles, hence ∠pab = ∠pba. subtracting, gives x = ∠pad−∠pab = ∠pbc −∠pba = 90◦. this is a preposterous conclusion – just where is the mistake in the "proof" and why does the argument break down there?

What kind of bond pays interest which is exempt from tax?

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?