What is the rhyme scheme of the third stanza of the poem?

Read the poem and answer the questions given below it.

The Clock Above the Blackboard

I sit at desk fourteen, beside the door,
two pens, a ruler, my admit card in line.
The papers lie face down on the teacher’s desk.
The clock above the blackboard says half past nine.

Ten minutes before the first bell rings,
and every minute lasts a year. I stare
up at the long hand above the board.
I look away, look back: it is still there.

The bell. The papers. I turn mine and read,
and soon my pen is moving at full speed.
Four answers done. I glance up at the wall:
an hour has gone, and I never felt it at all.

The sun lies in a yellow strip on my desk,
gold chalk dust drifts in the window light,
and the thin red second hand goes round and round,
sweeping the last ten minutes out of sight.

“Pens down,” the teacher says. The sheets are gone.
I look up at the clock above the board:
a dusty face, three minutes slow, as always,
the clock that all year we had ignored.