Font question in Metapost

[David Arnold <darnold@northcoast.com>]

All,

I have this file (see below) where I would like to make the font size of
all my math labels smaller, say 8pt instead of 10pt. Is there a simple way
to do this? I tried \scriptsize, but that was unsatisfactory when it came
to the matrices. What I really need is some sort of declaration to use a
smaller font. I am trying to do this in plain metapost.

input mp-tool;

beginfig(7);

%initialize scale
numeric u; 1u=1in;

%draw rectangles
path p, q;
p=unitsquare xyscaled(0.5u,1u) rotated 30;
draw p;
label(btex $\scriptstyle C(A)$ etex, center p);
q:=unitsquare xyscaled (0.5u,1u) rotated 120;
pair a;
a:=right*0.5u rotated 120;
q:=q shifted -a;
draw q;
label(btex $\scriptstyle N(A^T)$ etex, center q);

%label basis for C(A)
label.top(btex $B=\left\{\pmatrix{1\cr 0\cr 0},
  \pmatrix{0\cr 1\cr 0}\right\}$ etex, point 2 of p);

%label basis for N(A^T)
label.bot(btex $B=\left\{\pmatrix{0\cr 0\cr 1}\right\}$ etex, point 3 of q);

%save current picture
picture pic; pic:=currentpicture; currentpicture:=nullpicture;

%draw rectangles
path p, q;
p=unitsquare xyscaled(0.5u,1u) rotated -30;
pair a;
a:=right*0.5u rotated -30;
p:=p shifted -a;
draw p;
label(btex $\scriptstyle C(A^T)$ etex, center p);
q:=unitsquare xyscaled (0.5u,1u) rotated -120;
draw q;
label(btex $\scriptstyle N(A)$ etex, center q);

%label basis for C(A)
label.top(btex $B=\left\{\pmatrix{1\cr -1\cr  0\cr 0\cr 0},
  \pmatrix{0\cr 0\cr 1\cr 1\cr 1}\right\}$ etex, point 3 of p);

%label basis for N(A^T)
label.bot(btex $B=\left\{\pmatrix{1\cr 1\cr 0\cr 0\cr 0},
  \pmatrix{0\cr 0\cr -1\cr 1\cr 0},
  \pmatrix{0\cr 0\cr -1\cr 0\cr 1}\right\}$ etex, point 2 of q);

%bring back right-hand side
draw pic shifted (4u,0);
endfig;

end.