 * 3 + 0];
    const a21 = a[2 * 3 + 1];
    const a22 = a[2 * 3 + 2];
    const b00 = b[0 * 3 + 0];
    const b01 = b[0 * 3 + 1];
    const b02 = b[0 * 3 + 2];
    const b10 = b[1 * 3 + 0];
    const b11 = b[1 * 3 + 1];
    const b12 = b[1 * 3 + 2];
    const b20 = b[2 * 3 + 0];
    const b21 = b[2 * 3 + 1];
    const b22 = b[2 * 3 + 2];

    return [
      b00 * a00 + b01 * a10 + b02 * a20,
      b00 * a01 + b01 * a11 + b02 * a21,
      b00 * a02 + b01 * a12 + b02 * a22,
      b10 * a00 + b11 * a10 + b12 