Consider the following code snippet:

$```$

class BaseClass

$\{$

public:

BaseClass$()$;

virtual void set$\_$data$($int new$\_$data$1)$;

private:

int data$1$;

$\}$;

BaseClass::BaseClass$()$

$\{$

data$1=0$;

$\}$

void BaseClass::set$\_$data$($int new$\_$data$1)$

$\{$

cout $$ "BaseClass set$\_$data" $$ endl;

$\}$

class DerivedClass : public BaseClass

$\{$

public:

virtual void set$\_$data$($int new$\_$data$1)$;

$\}$;

void DerivedClass::set$\_$data$($int new$\_$data$1)$

$\{$

cout $$ "DerivedClass set$\_$data" $$ endl;

$\}$

int main$()$

$\{$

BaseClass$*$ bs$1=$ new BaseClass;

DerivedClass$*$ ds$1=$ new DerivedClass;

bs$1=$ ds$1$;

bs$1->$set$\_$data$(20)$;

return $\backslash$theta;

$\}$

$```$

What is the output?data$1\backslash (=20\backslash )$ is the output.

BaseClass set$\_$data is the output.

DerivedClass set$\_$data is the output.

There is no output because there are compilation errors.